Version of the Soyuz proposed with an Ariane 4 or Russian Lox/LH2 upper stage.

In order to achieve a payload double that of the current vehicle, it would seem a high-energy Lox/LH2 upper stage would be needed. Such an improvement was proposed as far back as July 1962 (the Molniya 8K78L) but never developed. The version with the Ariane 4 upper stage would be capable of putting 3900 kg into geosynchronous transfer orbit when launched from Kourou.

R-7 The world's first ICBM became the most often used and most reliable launch vehicle in history. The original core+four strap-on booster missile had a small third stage added to produce the Vostok launch vehicle, with a payload of 5 metric tons. Addition of a larger third stage produced the Voskhod/Soyuz vehicle, with a payload over 6 metric tons. Using this with a fourth stage, the resulting Molniya booster placed communications satellites and early lunar and planetary probes in higher energy trajectories. By the year 2000 over 1,628 had been launched with an unmatched success rate of 97.5% for production models. Improved models providing commercial launch services for international customers entered service in the new millenium, and a new launch pad at Kourou was to be inaugurated in 2011. It appeared that the R-7 could easily still be in service 70 years after its first launch. More...